Skip to main content

Consuming a REST Web Service returning JSON in APEX

Image
By
In APEX you can define a web service that returns XML as below - all declarative, just a few steps through a wizard.


Then generate a report on top of that web service - again just a few clicks through a wizard. The generated query looks like this:

select xtab."customerName"
     , xtab."customerId"
  from apex_collections c, 
          XMLTable('/Response/S_getCustomerListTableArray/S_getCustomerListArrayItem' passing xmltype001
            COLUMNS "customerName" PATH 'customerName'
                  , "customerId"   PATH 'customerId'
          ) xtab
 where c.collection_name = 'CUSTOMERLIST'

So the result of the web service is stored in an XMLTYPE column. And it's easy to spot where you're definitions for the Response XPath and Output Parameters are used.

But what if your web service returns JSON - as more and more web services will do so? If you switch the Output Format of the web service definition to JSON, the Response XPath property and the Output Parameters are not enterable. And if you generate a report on top of that web service, the resulting query is a - disappointing - 

select c.clob001
from apex_collections c
where c.collection_name = 'CUSTOMERLIST'

and your report will show a JSON dump. Not exactly what you're hoping for. And notice the result is stored in a CLOB.

But since 12c, the JSON support in the Oracle database has improved a lot and we can easily use that in our query. So if we rewrite our query to 

select cust.*
from   apex_collections
,      json_table(clob001, '$.Response.S_getCustomerListTableArray.S_getCustomerListArrayItem[*]'
       columns ( "customerName"   PATH '$.customerName'
               , "customerId"     PATH '$.customerId'
               )) cust
where collection_name = 'CUSTOMERLIST'

we will get the same result as the - old fashioned - XML one! And as you can see the code is very much alike and could be generated by APEX itself just like the XML version.

So I expect that in a future version this functionality will be added to the APEX builder - it shouldn't be that hard to implement! And maybe the apex_collections can have a real "JSON" column as well (in fact it would still be a CLOB with an "IS JSON" check).

The only prerequisite is, you have to run APEX on version 12c of the database. If you want to know more about JSON in the database, there is a serie of blog posts about this, starting here.
Labels:
Post a Comment

Popular posts from this blog

Refresh selected row(s) in an Interactive Grid

By
In my previous post I blogged about pushing changed rows from the dabatase into an Interactive Grid. The use case I'll cover right here is probably more common - and therefore more useful!

Until we had the IG, we showed the data in a report (Interactive or Classic). Changes to the data where made by popping up a form page, making changes, saving and refreshing the report upon closing the dialog. Or by clicking an icon / button / link in your report that makes some changes to the data (like changing a status) and ... refresh the report.  That all works fine, but the downsides are: The whole dataset is returned from the server to the client - again and again. And if your pagination size is large, that does lead to more and more network traffic, more interpretation by the browser and more waiting time for the end user.The "current record" might be out of focus after the refresh, especially by larger pagination sizes, as the first rows will be shown. Or (even worse) while you…
Read more

Push changed rows to an Interactive Grid

By
For pushing changes from the database to the end user, the regular solution is using websockets. A change in a record is detected - using a trigger or using the CQN (Change Query Notification) feature - and a notification is send to a websocket server. That websocket server broadcasts the notification over a channel to all browsers that are tuned in to that websocket channel. Then the browser reacts to that notification, usually showing an alert or refreshing a report. This trick is described on multiple sites, just Google for "oracle apex websockets" or similar.

So back in the old days, we used that notification in the browser to refresh the (interactive) report. But along comes the Interactive Grid (IG). While he full-refresh mechanism still works for IG, an IG has also the option to refresh just one row.  So wouldn't it be awesome that just the changed row(s) get refreshed upon a change in the database, instead of the whole report? Can we do it ... yes we can!
First i…
Read more

Dockerize your APEX development environment

By
Nowadays Docker is everywhere. It is one of the main components of Continuous Integration / Continuous Development environments. That alone indicates Docker has to be seen more as a Software Delivery Platform than as a replacement of a virtual machine.

However ...

If you are running an Oracle database using Docker on your local machine to develop some APEX application, you will probably not move that container is a whole to test and production environments. Because in that case you would not only deliver a new APEX application to the production environment - which is a good thing - but also overwrite the data in production with the data from your development environment. And that won't make your users very excited.
So in this set up you will be using Docker as a replacement of a Virtual Machine and not as a Delivery Platform.
And that's exactly the way Martin is using it as he described in this recent blog post. It is an ideal way to get up and running with an Oracle database …
Read more